This invention relates to dental radiation imaging systems, and in particular to systems for moving a radiation source and detector so as to produce panoramic images.
Panoramic dental radiation is used to obtain images of a patient's teeth in an orthogonal manner. Since the dental arch is not a circular shape, or often even any type of regular shape, the rotation of the arm to which the radiation source and detector are attached must be adjusted in the course of the imaging in order to achieve the proper orthogonal imaging. Conventional panoramic radiation apparatuses are characterized in that the radiation source is arranged to orbit about the patient's skull, whereby the dental arch can be imaged by means of a radiation detector orbiting on the opposite side of the skull. The function of the rotating mechanism of a panoramic radiation apparatus is to direct the radiation beam through the patient's jaw at a desired angle and to keep the radiation detector at a particular distance from the object being imaged.
The radiation source of the panoramic radiation system and the rotating mechanism of its radiation detector must be capable of forming an image of the dental arch. During the rotational movement, the center of rotation is moved in order to ensure orthgonality of the radiation beam on the dental arch, constant magnification and focus, and continuity of motion. The rotating mechanism must be able to accomplish the desired orbital movement of the center of rotation in a horizontal plane (or other plane as desired) and provide vertical support to the entire apparatus so that the desired orbit can be implemented with accuracy.
Such orbital movement can be achieved by virtue of different conventional rotating mechanisms. A combination of linear movement with rotational movement, such as that disclosed in U.S. Pat. No. 4,741,007, may be used. However, the movement has been found problematic due to the precise accuracy required of the orbital movement, that is, it is more difficult to obtain the same accuracy for the mechanism of the orbital movement when a linear movement is involved than when a rotational movement is employed alone.
In U.S. Pat. No. 6,466,641, rotational movement is accomplished using orbital movement of several body parts of the system operating independently from each other. This system is very complicated and expensive.
The present invention relates to improvements to the apparatus described above and to solutions to some of the problems raised or not solved thereby.